1). Field of the Invention
This invention relates to a panoramic imaging arrangement of the kind capable of capturing, focusing, correcting aberrations and otherwise manipulating light received from a 360xc2x0 surrounding panoramic scene, and to a method of capturing a 360xc2x0 surrounding panoramic scene.
2). Discussion of Related Art
Panoramic imaging arrangements have become popular in recent years for purposes of viewing 360xc2x0 surrounding panoramic scenes. Older generations of panoramic imaging arrangements generally consisted of revolving periscope-like constructions having relatively complex mechanisms for revolving them. More recently, stationary panoramic imaging arrangements have been developed. A stationary panoramic imaging arrangement generally has one or more lenses, each having a vertically extending axis of revolution, which are used to refract or reflect light received from a 360xc2x0 surrounding panoramic scene. The lenses alter the direction of the light, whereafter the light passes through a series of lenses which are located vertically one above the other and which further manipulate the light by, for example, focusing the light or altering the intensity of the light.
The task of receiving light in a sideways direction and altering the direction of the light so that the light then proceeds in a vertical direction is a difficult one. Altering the direction of light to such a degree, especially when coming from a 360xc2x0 surrounding scene, oftentimes leads to aberrations in the resulting light. These aberrations may include astigmatism of the light, defects in color of the light, a loss of image plane flatness, and other defects, some of which are discussed in more detail herein below.
Relatively complex lenses and lens arrangements have been developed in order to overcome these aberrations. Some of these lenses have surfaces which are aspherical (see for example U.S. Pat. No. 5,473,474 issued to Powell). Aspherical lenses are difficult to manufacture and therefore less practical to manufacture than for example spherical lenses.
One reason why aberrations in light occur is due to the use of refractive lenses instead of reflective lenses. The use of refractive lenses results in aberrations in color of the resulting light, whereas the use of reflective, or mirror lenses does not result in, or cause minimal aberrations in color of the light reflected from them. One reason for the lack of the use of reflective lenses, on the other hand, is that reflective lenses, when exposed to the environment, degrade through time, resulting in loss of image.
These and other aberrations in light are more prominent when light is received from a panoramic view at a relatively large lateral included angle, particularly if the included angle, in a vertical plane, is larger than 90xc2x0 and especially if the included angle extends from an angle below the horizon to an angle above the horizon, i.e. covering substantially more than a hemisphere.
Another problem with typical panoramic imaging arrangements is that they only allow for capturing of a view in narrow lateral angle. It may therefore be advantageous also to capture a scene, perhaps of the sky, located above the field of view captured by typical panoramic imaging arrangements.
According to one aspect of the invention there is provided a panoramic imaging arrangement comprising lens block and a system of lenses. The lens block has a substantially vertical axis of revolution and is capable of receiving light from a first, 360xc2x0 surrounding panoramic scene. The system of lenses has a vertical axis of revolution substantially coinciding with the axis of revolution of the lens block and is positioned to receive light from a second scene which is at least partially located above the first, surrounding panoramic scene, and projecting the light from the second scene.
The lens block is typically a refractive lens and may have a convex lower surface through which light from the first, surrounding panoramic scene enters the lens block.
The lens block may have a convex upper reflective surface from which light from the first, surrounding panoramic scene is downwardly reflected. An opening may be formed in the convex upper reflective surface through which light from the second scene may pass after leaving the system of lenses.
Light from the second scene may pass through the lens block after leaving the second lens.
The lens block preferably receives light from the first, surrounding panoramic scene for an unbroken included angle, in a plane of the axis of revolution, which preferably is at least 60xc2x0, and more preferably at least 90.
The system of lenses may receive light from the second scene for an unbroken included angle, in a plane of the axis of revolution, which is preferably at least 60xc2x0 and more preferably at least 80xc2x0.
Preferably, the lens block receives light from the first, surrounding panoramic scene for an unbroken included angle, in a plane of the axis of revolution, and the system of lenses receives light from the second scene for an unbroken included angle, in the plane of the axis of revolution, wherein twice the unbroken included angle received by the lens block and the unbroken included angle received by the system of lenses amount to at least 220xc2x0.
The panoramic imaging arrangement preferably further includes at least one additional set of lenses through which light from both the first, surrounding panoramic scene and light from the second scene passes after leaving the lens block and the system of lenses respectively.
The panoramic imaging arrangement may further include image capturing apparatus positioned to receive light from both the first, surrounding panoramic scene and from the second scene after passing through the additional set of lenses.